In my aforesaid prior application, I disclose earphone apparatus in which an earmold is coupled through a main sound tube to a base unit which is of compact form and which includes a miniature receiver with a sound outlet connected to the end of the main sound tube and also to acoustic resonance cancellation means within the base unit. The base unit also includes an electrical response-equalization network which augments the effect of the acoustic elements to obtain frequency response characteristics which are not obtained with conventional audiometry earphones and which are highly desirable. One characteristic is a substantially flat response over a frequency range extending from less than 50 Hz to more than 10,000 Hz. Another frequency response characteristic obtained is one that closely matches the diffuse-sound-field response of the normal external ear.